POWER SUPPLY DEVICE OF A VEHICLE WITH A VOLTAGE UPGRADE IN CONTINUOUS OR INTERMITTENT OPERATION

Abstract

Power supply unit of a vehicle with a power generation unit (100, 110); a power storage device (150); a voltage boost converter (200) that increases the voltage of the power storage device (150), wherein the voltage boost converter (200) supplies the increased voltage to an electrical load (210, 200) of the vehicle; and a control device (500) that controls the voltage booster (200) in a continuous voltage boosting mode and an intermittent voltage boosting mode, wherein in the continuous voltage boosting mode the voltage booster (200) is operated continuously and in the intermittent voltage boosting mode the voltage booster (200) is operated intermittently, wherein the control device (500) estimates a state of charge (SOC) of the power storage device (150) based on a current flowing into and out of the power storage device and the control device (500) instructs the power generation unit (100, 110) to charge the power storage device (150) when an estimated state of charge is lower than a predetermined lower limit (LL), wherein the control device (500) suppresses operation of the voltage boost converter (200) in the intermittent voltage boost mode in a case where the estimated value is equal to or less than a predetermined threshold (K1) that is greater than the lower limit (LL).

Description

Technical field

[0001] The present invention relates to a power supply unit for a vehicle with a voltage boost converter in continuous or intermittent operating mode. State of the art

[0002] A power supply system for a hybrid vehicle is known that boosts a low output voltage from a battery using a voltage booster and supplies electrical power from the boosted voltage to a motor-generator. A technique for reducing the electrical power loss of the voltage booster has been proposed for such a power supply system.

[0003] For example, a hybrid vehicle disclosed in Japanese Patent Publication No. JP 2010-11651A (PTL 1) has first and second batteries, a first voltage booster that converts an output voltage of the first battery to output the converted voltage to a motor-generator, and a second voltage booster that converts an output voltage of the second battery to output the converted voltage to the motor-generator. When the vehicle is operating in hybrid mode, a control device operates the first voltage booster while deactivating the second voltage booster. This reduces electrical power loss in the second voltage booster and thus improves fuel economy. List of patent literature PTL 1: JP 2010 - 11 651 A PTL 2: JP 2012 - 222 907 A PTL 3: JP 2011 - 15 603 A

[0004] Document US 2010 / 0045103A1 discloses a control device for a load device mounted in a vehicle. The control device operates an inverter when an applied voltage is equal to or less than a predetermined upper limit and stops the inverter when the applied voltage exceeds the upper limit. The upper limit is set based on the temperature dependence of the withstand voltage of an IGBT element contained in the inverter and a detected temperature.

[0005] German patent application DE 11 2010 002 433 T5 discloses a control device that controls a transformer according to a total load imposed on a load-drive system including the transformer and a load. The control device comprises: a switching control unit that performs the switching control of the transformer; a load power derivation unit that derives load power; and a transformer loss reduction derivation unit that derives a reduction amount of the loss generated in the transformer, based on the load power derived by the load power derivation unit and a transformation ratio of the transformer when the switching control unit performs intermittent control of the transformer.a derivation unit for a load loss increase amount, which derives an increase in the amount of loss generated in the load when the switching control performs intermittent control of the transformer; and a control command unit which instructs the switching control to perform intermittent control of the transformer when the reduction amount of transformer loss, derived from the derivation unit for the transformer loss reduction amount, is greater than the increase amount, derived from the derivation unit for the load loss increase amount.

[0006] Publication JP 2010-119 175 A discloses a DC-DC converter in which capacitors can be rapidly discharged by controlling the switching elements of the DC-DC converter when the system is stopped. The discharged charge is then converted into heat.

[0007] Document US 2012 / 0049774A1 discloses a control device for a voltage converter. In the voltage converter, a first switching element or a second switching element is selected according to a current flowing through an inductor. The voltage converter is then controlled such that a drive command is generated for the selected switching element. Summary of the invention: Technical problem

[0008] In cases where the electrical power consumption of a motor-generator is low, intermittent voltage boost control can be implemented by intermittently operating and stopping a boost converter to reduce electrical power loss due to the converter's switching. With this control, the current flowing through the boost converter and the current flowing to / from a battery (battery current) also switch rapidly between a flowing and a non-flowing state.

[0009] Depending on the configuration of an ECU (electronic control unit) that performs vehicle control, electrical current data used for control may be measured in slow cycles, resulting in a failure to observe precise changes in electrical current.

[0010] More precisely, the ECU can use a method to estimate the state of charge (SOC) of a battery by integrating the battery current. However, when this estimation method is used under intermittent voltage boost control, changes in battery current cannot be precisely observed, thus reducing the accuracy with which the SOC is estimated. This reduced accuracy can cause the estimated SOC value to deviate from the true value. Consequently, charging the battery may be forced even when it is unnecessary. In such a case, fuel economy can be negatively impacted.

[0011] One object of the present invention is to provide a power supply device for a vehicle that is able to ensure an effect of reducing electrical power loss through intermittent voltage boost control, and is still able to prevent a deterioration in fuel economy. Solution to the problem

[0012] This problem is solved by a power supply device as specified in claim 1.

[0013] According to claim 1, the control device suppresses the operation of the voltage boost converter in the intermittent voltage boost mode in a case where the estimated value is equal to or less than a predetermined threshold that is greater than the lower limit.

[0014] According to the characteristics described above, the threshold can be set to suppress operation in the intermittent voltage boost mode when the estimated value is in the range between the lower limit and the threshold.

[0015] Preferably, the threshold is determined such that the threshold is greater than the lower limit by a maximum error of the estimated value that can be caused by the operation of the voltage boost converter in the intermittent voltage boosting mode.

[0016] Based on the characteristics described above, the voltage value is set with a margin of error of a maximum estimated value from the lower limit. This reliably prevents the need for forced charging.

[0017] Preferably, the control device suppresses the operation of the voltage boost converter by preventing the operation of the voltage boost converter in the intermittent voltage boosting mode.

[0018] According to the characteristics described above, operation in the intermittent voltage boost mode is prevented. Therefore, compared to the case where the intermittent voltage boost mode is suppressed, it can be reliably prevented that the control device incorrectly determines that the estimated value is less than the lower limit.

[0019] Preferably, the control device suppresses the operation of the voltage boost converter by reducing the rate at which the voltage of the power storage device is increased in the intermittent voltage boosting mode.

[0020] According to the characteristics described above, reducing the rate at which the voltage of the power storage device is increased causes the battery current to gradually rise. Therefore, compared to a higher voltage increase rate, an average battery current is calculated over time. This reduces the variation in the battery current value depending on the timing of the current measurement, thus improving the accuracy with which the state of charge of the power storage device is estimated. Consequently, the unnecessary need for forced charging of the power storage device can be avoided. Additionally, the power loss of the voltage boost converter due to forced charging can be reduced.

[0021] Preferably, the control device suppresses the operation of the voltage boost converter by limiting the current flowing through the voltage boost converter in the intermittent voltage boosting mode to a predetermined value or less.

[0022] As described above, limiting the current flowing through the voltage boost converter allows for a limitation of the battery current. The battery current thus increases gradually. Compared to a higher voltage boost rate, an average battery current is calculated over time. This reduces the variation in the battery current value depending on the current measurement time, thereby improving the accuracy of estimating the state of charge of the power storage device. Consequently, unnecessary forced charging of the power storage device can be avoided. Advantageous effects of the invention

[0023] According to the present invention, the intermittent voltage boost control can ensure a reduction in electrical power loss while still preventing a deterioration in fuel economy. Brief description of the drawings Fig. Figure 1 shows a block diagram illustrating an example configuration of a hybrid vehicle, which is shown as a typical example of an electrically powered vehicle, according to an embodiment of the present invention. Fig. Figure 2 shows a circuit diagram representing an example configuration of an electrical system of the in Fig. Illustrated by the hybrid vehicle shown in Figure 1. Fig. Figure 3 shows a signal waveform diagram to illustrate a battery current IB in the case where a converter 200 is controlled by the intermittent voltage boosting mode. Fig. Figure 4 shows a diagram illustrating the control of the converter 200 as a function of the SOC of a battery 150. Fig. Figure 5 shows a flowchart illustrating a procedure for voltage boost control by the converter 200. Fig. Figure 6 shows a flowchart detailing step ST25 in the flowchart of Fig. 5 illustrates. Fig. Figure 7 shows a signal waveform diagram to illustrate operation in a continuous voltage boost mode and operation in an intermittent voltage boost mode. Fig. Figure 8 shows a representation comparing the battery current IB as a function of a recovery rate. Description of exemplary implementations

[0024] Exemplary embodiments of the present invention are described in detail below with reference to the drawings. The same or corresponding parts are designated by the same reference numerals in the drawings, therefore their description will not be repeated. First embodiment

[0025] Fig. Figure 1 shows a block diagram illustrating an example configuration of a hybrid vehicle, which is shown as a typical example of the electrically powered vehicle, according to an embodiment of the present invention.

[0026] According to Fig. The hybrid vehicle comprises a power engine 100, a first motor generator (MG) 110, a second motor generator (MG) 120, a power distribution device 130, a reduction gearbox 140, a battery 150, drive wheels 160, and a control device 500. The control device 500 is configured to include a power management ECU (electronic control unit) 170 and a motor generator ECU 172.

[0027] Driving the hybrid vehicle is effected by a drive force from the power unit 100 and / or the second motor unit 120. The power unit 100, the first motor unit 110, and the second motor unit 120 are coupled to each other by the power distribution device 130.

[0028] The power distribution device 130 is typically configured as a planetary gear mechanism. The power distribution device 130 comprises a sun gear 131, which is an external gear, a ring gear 132, which is an internal gear, arranged concentrically with the sun gear 131, a plurality of pinions 133 meshing with the sun gear 131 and the ring gear 132, and a carrier 134. The carrier 134 is configured to hold a plurality of the pinions 133 so that they can rotate on their respective axes and also rotate.

[0029] The power distribution device 130 divides the kinetic power generated by the power machine 100 into two paths. One path is for driving drive wheels 160 via the reduction gear 140. The other is for generating electrical power by driving the first machine gun 110.

[0030] The first MG 110 and the second MG 120 are each typically a rotating three-phase alternating current electric machine configured in the form of a permanent magnet motor.

[0031] The first MG 110 primarily functions as an "electric generator" and is capable of generating electrical power from a motive force supplied by the engine 100 and divided by the power distribution device 130. The engine 100 and the first MG 110 thus constitute a "power generation unit." The electrical power generated by the first MG 110 is used differently depending on the vehicle's operating conditions and the state of charge (SOC) of the battery 150. The voltage of this electrical power is adjusted by a converter, described below, and stored in the battery 150. For example, when the engine 100 is driven by the motor during startup, the first MG 110 can also operate as an electric motor as a result of torque control.

[0032] The second MG 120 primarily functions as an "electric motor" and is powered by the electrical power stored in the battery 150 and / or the electrical power generated by the first MG 110. The power generated by the second MG 120 is transferred to a drive shaft 135 and then, via the reduction gear 140, to the drive wheels 160. Thus, the MG 120 assists the power unit 100 or causes the vehicle to move due to the power generated by the second MG 120.

[0033] When the hybrid vehicle is regeneratively braked, the second MG120 is driven by the drive wheels 160 via the reduction gear 140. In this case, the second MG120 acts as an electric generator. Thus, the second MG120 serves as a regenerative brake, converting braking energy into electrical power. The electrical power generated by the second MG120 is stored in the battery 150.

[0034] The battery 150 is a battery pack composed of multiple battery modules connected in series. Each battery module consists of multiple battery cells integrated within it. The voltage of the battery 150 is approximately 200V. The battery 150 can be charged with electrical power generated by either the first MG 110 or the second MG 120. The temperature, voltage, and current of the battery 150 are monitored by a battery sensor 152. A temperature sensor, a voltage sensor, and a current sensor are collectively referred to as the battery sensor 152.

[0035] The PM-ECU 170 and the MG-ECU 172 are each configured to include a CPU (central processing unit) and (not shown) memory. They are configured to perform operations based on values ​​acquired by the sensors, through software processing according to a map and a program stored in the memory. Alternatively, at least part of the PM-ECU 170 and the MG-ECU 172 can be configured to perform a predetermined mathematical operation and / or a predetermined logical operation through hardware processing by a dedicated electronic circuit or the like.

[0036] The power unit 100 is controlled according to an operating command value from the PM-ECU 170. The first MG 110, the second MG 120, the converter 200, and the inverters 210 and 220 are controlled by the MG-ECU 172. The PM-ECU 170 and the MG-ECU 172 are connected in such a way that they can communicate bidirectionally with each other.

[0037] Although, according to the present embodiment, the PM-ECU 170 and the MG-ECU 172 are configured as separate ECUs, a single ECU can be provided which contains the respective functions of these ECUs.

[0038] Fig. Figure 2 shows a circuit diagram representing an example configuration of an electrical system of the in Fig. Illustrated by the hybrid vehicle shown in Figure 1.

[0039] According to Fig. 2 The electrical system of the hybrid vehicle includes the converter 200 (voltage boost converter), the inverter 210 associated with the first MG 110, the inverter 220 associated with the second MG 120, an SMR (system main relay) 230 and capacitors C1 and C2.

[0040] The converter 200 has two power semiconductor switching elements Q1 and Q2 (hereinafter also referred to simply as "switching elements") connected in series, diodes D1 and D2, which are provided in association with the switching elements Q1 and Q2 respectively, and an inductor L.

[0041] Switching elements Q1 and Q2 are connected in series between a positive line PL2 and a ground line GL, which is connected to a negative electrode of battery 150. The collector of switching element Q1 is connected to the positive line PL2, and the emitter of switching element Q2 is connected to the ground line GL. Diodes D1 and D2 are connected antiparallel to switching elements Q1 and Q2, respectively. Switching element Q1 and diode D1 form an upper branch of converter 200, and switching element Q2 and diode D2 form a lower branch of converter 200.

[0042] Suitable power semiconductor switching elements Q1 and Q2 include an IGBT (individualized gate bipolar transistor), a power MOS (metal oxide semiconductor) transistor, a power bipolar transistor, and similar devices. The ON / OFF status of each switching element Q1 and Q2 is controlled by a switching control signal from the MG-ECU 172.

[0043] One end of the choke coil L is connected to a positive line PL1, which is connected to a positive electrode of the battery 150, and the other end is connected to a connection node of the switching elements Q1 and Q2, namely a connection point between the emitter of the switching element Q1 and the collector of the switching element Q2.

[0044] Capacitor C2 is connected between the positive line PL2 and the ground line GL. Capacitor C2 smooths an AC component of any voltage variation between the positive line PL2 and the ground line GL. Capacitor C1 is connected between the positive line PL1 and the ground line GL. Capacitor C1 smooths an AC component of any voltage variation between the positive line PL1 and the ground line GL.

[0045] Furthermore, an air conditioner (A / C) 240 is connected between the positive line PL1 and the ground line GL. Although not shown, an auxiliary machine other than the air conditioner 240 may also be connected between the positive line PL1 and the ground line GL. The current supplied to the air conditioner 240 and the current supplied to the auxiliary machine are collectively expressed as the auxiliary machine current Idc.

[0046] A current IL flowing in the choke coil L (hereinafter referred to as choke coil current) is detected by a current sensor SEIL. A voltage sensor 180 detects a terminal voltage of capacitor C2, which is an output voltage of the converter 200, namely a voltage VH (system voltage) between the positive line PL2 and the ground line GL, and outputs the detected value to the MG-ECU 172.

[0047] The converter 200, the inverter 210 and the inverter 220 are connected to each other by the positive line PL2 and the ground line GL.

[0048] In voltage boost mode, converter 200 boosts a DC voltage VB (voltage across the opposite terminals of capacitor C1), which is supplied from battery 150, and applies the system voltage VH generated by the voltage boost to inverters 210 and 220. More precisely, in response to a switching control signal from the MG-ECU 172, an ON period of switching element Q1 and an ON period of switching element Q2 are alternated, and a voltage boost ratio is determined depending on a ratio between these ON periods.

[0049] In a voltage-step-down mode, the converter 200 reduces the system voltage VH, which is supplied from the inverters 210 and 220 via capacitor C2, to charge the battery 150 with this voltage. More precisely, in response to a switching control signal from the MG-ECU 172, a period in which only switching element Q1 is ON and a period in which both switching elements Q1 and Q2 are OFF are alternated, and a voltage-step-down ratio is determined depending on the duty cycle of the ON period.

[0050] When the voltage boost / dip operation of the converter 200 is stopped, the switching element Q1 is fixed in an ON state and the switching element Q2 is fixed in an OFF state.

[0051] The inverter 210 is configured as a general three-phase inverter and has a U-phase branch 15, a V-phase branch 16, and a W-phase branch 17. Branches 15 to 17 have switching elements Q3 to Q8 and antiparallel diodes D3 to D8.

[0052] When the vehicle is moving, the inverter 210 controls the current or voltage from each phase coil of the first MG 110 such that the first MG 110 operates according to an operating command value (typically a torque command value) set to generate a driving force (vehicle propulsion force, electrical power generation torque, or the like) required for the vehicle to move. Specifically, the inverter 210 performs a bidirectional DC / AC power conversion between the positive line PL2 and the first MG 110.

[0053] Inverter 220, like inverter 210, is configured as a general three-phase inverter. When the vehicle is moving, inverter 220 controls the current or voltage from each phase coil of the second MG 120 such that the second MG 120 operates according to an operating command value (typically a torque command value) set to generate a driving force (vehicle propulsion force, regenerative braking torque, or the like) required to move the vehicle. Inverter 220 performs a bidirectional DC / AC power conversion between the positive line PL2 and the second MG 120.

[0054] The PM-ECU 170 calculates a torque command value TR1 for the first MG110 and a torque command value TR2 for the second MG 120 based on an accelerator pedal position Acc and a speed V of the hybrid vehicle.

[0055] The MG-ECU 172 calculates an optimal value (setpoint) for the output voltage (system voltage) VH of the converter 200, namely a command voltage VH*, based on a torque command value TR1 for the first MG 110 and a torque command value TR2 for the second MG 120, which are calculated by the PM-ECU 170, as well as a motor speed MRN1 of the first MG 110 and a motor speed MRN2 of the second MG 120. Based on the output voltage VH of the converter 200, which is detected by the voltage sensor 180, and the command voltage VH*, the MG-ECU 172 calculates a duty cycle to control the output voltage VH such that the voltage VH equals the command voltage VH*, and controls the converter 200 accordingly.

[0056] The MG-ECU 172 controls the converter 200 by setting it to either a continuous voltage boost mode or an intermittent voltage boost mode. In continuous voltage boost mode, the converter 200 performs a voltage boost operation without stopping. In intermittent voltage boost mode, the converter 200 intermittently repeats the voltage boost operation and stops. When the converter 200 performs the voltage boost operation, switching elements Q1 and Q2 are switched between an ON state and an OFF state. When the converter 200 stops the voltage boost operation, switching element Q1 is fixed in the ON state and switching element Q2 is fixed in the OFF state.

[0057] The fact that the converter 200 does not increase the voltage in the continuous voltage boost operating mode, and the fact that the converter 200 stops the voltage boosting in the intermittent voltage boost operating mode, differ from each other in the following respect.

[0058] In continuous voltage boost mode, the voltage of battery 150 is supplied to inverters 210 and 220 via converter 200. Therefore, if converter 200 does not boost the voltage in continuous voltage boost mode, the voltage of battery 150 is supplied unchanged to inverters 210 and 220 via converter 200 (duty cycle 1), without being boosted.

[0059] In contrast, if the converter 200 stops the voltage boosting in the intermittent voltage boosting mode, the voltage of the battery 150 is not supplied to the inverters 210 and 220 by converter 200.

[0060] The control device 500 (in particular the PM-ECU 170) estimates the state of charge (SOC) of the battery 150 by integrating the battery current IB. Since a general method can be used to estimate the SOC by integrating the current, its description is not repeated here. However, it should be noted that the present embodiment has a feature such that the battery current IB varies rapidly under the control in the intermittent voltage boost mode.

[0061] Fig. Figure 3 shows a signal waveform diagram illustrating the battery current IB in the case where the converter 200 is controlled in intermittent voltage boost mode. According to Fig. 3. During intermittent voltage boost control, the battery current IB varies in very short cycles (e.g., 3 to 5 ms). To accurately observe the current, it is necessary that the cycles in which the current is measured are sufficiently shorter than the cycles in which the current varies.

[0062] However, to shorten the cycles in which the current is measured, it is necessary to use a high-speed CPU or increase the communication frequency, which increases costs. Therefore, in the present embodiment, the control device 500 uses a CPU with control cycles that are longer than the cycles in which the battery current IB varies. For example, the control cycle period of the CPU of the control device 500 is approximately 8 ms, compared to the battery current IB cycle period of approximately 5 ms.

[0063] As described above, if the time intervals at which the battery current IB is measured are longer than the intervals at which the battery current IB varies, the current cannot be observed accurately. Therefore, the accuracy with which the battery current IB is measured is lower under control in the intermittent voltage boost mode. Consequently, the accuracy with which the state of charge (SOC) is estimated may be lower, and the estimated SOC value may deviate from the true value. Specifically, when the control device 500 operates in the intermittent voltage boost mode, it controls the converter 200 based on the relatively lower accuracy of the estimated SOC, thus charging or discharging the battery 150.

[0064] Fig. Figure 4 shows a diagram illustrating the control of the converter 200 as a function of the state of charge (SOC) of the battery 150. Fig. Figure 4 represents the horizontal axis as the SOC of battery 150, and the vertical axis as the open circuit voltage (OCV) of battery 150.

[0065] An upper limit (UL) and a lower limit (LL) of the state of charge (SOC) of battery 150 are defined. If the SOC exceeds the upper limit (UL), the voltage (VB) of battery 150 rises sharply with the increase in SOC. Therefore, if the SOC exceeds the upper limit (UL), the control device 500 controls the converter 200 to discharge the battery in order to protect battery 150.

[0066] In contrast, if the state of charge (SOC) is lower than the lower limit LL, the voltage VB 150 decreases sharply with the decrease in SOC. Therefore, if the SOC is lower than the lower limit LL, the control device 500 controls the converter 200 such that the battery 150 is charged. In other words, the control device 500 estimates the SOC of battery 150 based on the battery current IB flowing into / out of battery 150 and forces battery 150 to be charged by the power unit 100 and the first motor unit 110 if the estimated SOC is lower than the predetermined lower limit LL.

[0067] Below, a discharge that is performed when the SOC is higher than the upper limit UL is referred to as a forced discharge, and a charge that is performed when the SOC is lower than the lower limit LL is referred to as a forced charge.

[0068] If the estimated SOC value deviates from the true value as described above, the control device 500 might erroneously determine that the estimated SOC value is higher than the upper limit (UL), even though the true SOC value is sufficiently lower than the UL. In this case, a forced discharge is performed to cause the SOC to drop sharply. As a result, a user may get an abnormal impression that the SOC has decreased unnaturally, which might be detected, for example, by a change in a display that indicates the SOC.

[0069] Conversely, it could also occur that the control device 500 incorrectly determines that the estimated SOC value is lower than the lower limit LL, despite the fact that the true SOC value is sufficiently higher than the lower limit LL. In this case, a forced charging is performed to cause the engine 100 to be activated. Since the engine 100 is activated in this case based on the incorrect determination, there is a possibility that fuel economy will be worsened. Additionally, because the operation of the engine 100 is started at an unintended time, the user may have an abnormal impression of the engine's operation.

[0070] With regard to the above, the thresholds K1 and K2 are defined between the lower limit LL and the upper limit UL. Threshold K1 is defined between the lower limit LL and a central value C, and threshold K2 is defined between the central value C and the upper limit UL (K1 < C < K2). The central value C is, for example, an average of the upper limit UL and the lower limit LL. As long as the central value C is a value between the upper limit UL and the lower limit LL, the central value is not limited to the average.

[0071] Furthermore, the threshold K1 is preferably a value determined by adding an error dSOC of the SOC, which is assumed to occur under control in the intermittent voltage boost mode, to the lower limit LL of the SOC. In other words, the threshold K1 is determined such that it is greater than the lower limit LL by a maximum error (dSOC) of the estimated value of the SOC that can be caused by the operation of the converter 200 in the intermittent voltage boost mode. Likewise, the threshold K2 is preferably a value determined by subtracting the error dSOC from the upper limit UL of the SOC. The method for determining the error dSOC is described in detail below.

[0072] If the state of charge (SOC) falls within the range defined by thresholds K1 and K2 (i.e., if the SOC is equal to or greater than threshold K1 and lower than threshold K2), intermittent voltage boosting operation is permitted. Conversely, if the SOC is outside this range (i.e., if the SOC is lower than threshold K1 or higher than threshold K2), intermittent voltage boosting operation is prevented, and continuous voltage boosting operation is implemented. The range described above is also referred to as the allowable range.

[0073] The range of the SOC that is greater than the threshold K1 and equal to or less than the central value C is a generally used range, in contrast to the range that is greater than the lower limit LL and equal to or less than the threshold K1. The allowable range is defined in this way, and accordingly, if the SOC is within the generally used range, the operation of the converter 200 in intermittent voltage boost mode is permitted. Conversely, if the SOC is within the range that is not generally used (the range that is greater than the lower limit LL and equal to or less than the threshold K1), the operation of the converter 200 intermittent voltage boost mode is suppressed.The range of the SOC in which the operation of the voltage boost converter in the intermittent voltage boosting mode is suppressed can be limited to the range that is not generally used.

[0074] Fig. Figure 5 shows a flowchart illustrating a procedure of voltage boost control by the converter 200. Fig. Figure 7 shows a signal waveform diagram to illustrate operations in the continuous voltage boost mode and the intermittent voltage boost mode.

[0075] Fig. Figure 7(a) shows a diagram illustrating an output voltage (system voltage) VH of the converter 200 in the continuous voltage boosting mode and the intermittent voltage boosting mode. Fig. Figure 7(b) shows a diagram illustrating the inductor current IL in the continuous voltage boost mode and the intermittent voltage boost mode. Although switching of converter 200 causes the inductor current IL to vary, the diagram shows Fig. 7(b) the choke coil current, the varying component of which is smoothed due to switching. Fig. Figure 7(c) shows a diagram illustrating a voltage boost power loss LP due to switching in the continuous voltage boost mode and the intermittent voltage boost mode.

[0076] According to Fig. 2, Fig. 4 and Fig. In step ST10, the control device 500 sets the converter 200 to continuous voltage boosting mode. The converter 200 performs the voltage boosting operation without stopping.

[0077] Subsequently, if the average value ILM of the choke current IL over a predetermined period in the past is lower than a threshold TH1 in step ST20, the control device 500 causes the process to proceed to step ST25. In step ST25, the control device 500 checks the battery condition to determine whether or not the intermittent voltage boost mode should be allowed.

[0078] Fig. Figure 6 shows a flowchart detailing step ST25 of the flowchart according to Fig. 5 illustrated. Fig. 2 and Fig. 6. In response to the start of the process in step ST25, the control device 500 receives the battery current IB from the battery sensor 152 and integrates the battery current IB to calculate an estimated value of the state of charge (SOC) of battery 150 in step ST100. The control device 500 then determines whether the SOC of battery 150 is within the permissible range (the range between the thresholds K1 and K2 according to...). Fig. 4) falls or does not.

[0079] In the event that the SOC is outside the allowable range in step ST100, the control device 500 causes the process to proceed to step ST110 to determine that the intermittent voltage boost mode is suppressed, and causes the process to proceed to step ST10 according to the flowchart of Fig. 5 returns. In this case, the converter 200 is set to operate in continuous voltage boost mode.

[0080] In other words, when the estimated value of the SOC is closer to the lower limit LL, the control device 500 suppresses the operation of the converter 200 in the intermittent voltage boost mode to a greater extent. According to the present embodiment, the control device 500 suppresses the operation of the converter 200 by preventing the converter 200 from operating in the intermittent voltage boost mode.

[0081] In contrast, if the SOC falls within the allowable range in step ST100, the control device 500 causes the process to proceed to step ST120 to determine that the intermittent voltage boost mode is allowed, and causes the process to proceed to step ST30 in the flowchart according to Fig. 5. In this case, the converter 200 is set to operate in intermittent voltage boost mode.

[0082] In step ST30, the control device 500 sets the converter 200 to intermittent voltage boosting mode. When the converter is set to intermittent voltage boosting mode, the control device 500 first stops the voltage boosting operation of the converter 200 (see, for example, time (1) in Fig. 7) It should be noted that the voltage boost mode can be stopped immediately after the converter has been switched to the intermittent voltage boost mode, or after a predetermined time has elapsed. As long as the condition in which voltage boosting is permitted and the condition in which voltage boosting is prohibited are repeated, this operation is contained in the intermittent voltage boost mode.

[0083] When the voltage boost operation of converter 200 is stopped, no current is output from battery 150. Therefore, the inductor current IL is zero, and the voltage boost power loss LP is zero. While the voltage boost operation of converter 200 is stopped, the first MG 110 and / or the second MG 120 are driven by electrical power stored in capacitor C2. When electrical charge is discharged from capacitor C2, the system voltage VH decreases.

[0084] Subsequently, if a deviation |VH*-VH| between the system voltage VH and the command voltage VH* is equal to or greater than a limit value dVH in step ST40, the control device 500 causes the process to proceed to step ST50. In step ST50, the control device 500 causes the converter 200 to restart the voltage boost operation (see, for example, time (2) in Fig. 7).

[0085] When the voltage boost operation is restarted by the converter 200, the battery 150 supplies current (recovery current) required to drive the first MG 110 and / or the second MG 120 while capacitor C2 is being charged. Therefore, the choke current IL is increased, and the voltage boost power loss LP is also increased.

[0086] Then, when the system voltage VH equals the command voltage VH* in step ST60, the control device 500 causes the process to proceed to step ST70. In step ST70, the control device 500 causes the voltage boost operation by the converter 200 to be stopped (see, for example, time (3) in Fig. 7) After step ST70, the process is repeated from step ST40.

[0087] If the average ILM of the choke current IL over a predetermined period in the past is greater than a threshold TH2 in step ST80, the control device 500 causes the process to proceed to step ST90 to put the converter 200 into continuous voltage boost mode. The converter 200 performs the voltage boost operation without stopping (see, for example, time (4) in Fig. 7) At that time (4) in Fig. Figure 7 shows that the command voltage VH* has been increased and the choke current IL begins to increase. After step ST90 has been performed, the sequence of process steps ends according to Fig. 5.

[0088] Fig. Figure 7(c) shows the reduction in voltage boost power loss LP during a period of time when voltage boosting is stopped and a subsequent period when voltage boosting is performed in the intermittent voltage boosting mode. An area P3 of a region enclosed by a line representing a reference power loss BS and a line representing a voltage boost power loss LP that is higher than the reference power loss BS line is the sum of the voltage boost power losses LP that are greater than the voltage boost loss in the continuous voltage boosting mode.An area P0 of a region enclosed by a line representing the reference power loss BS and the line representing the voltage boost power loss LP, which lies below the reference power loss BS line, is the sum of the voltage boost power losses LP that are smaller than the voltage boost power loss in continuous voltage boost mode. A value P1, determined by subtracting P2 (=P3) from P0, is the sum of reductions in voltage boost power loss with respect to the voltage boost loss in continuous voltage boost mode achieved by operating in intermittent voltage boost mode, consisting of a period during which voltage boosting is stopped and a subsequent period during which voltage boosting is performed.

[0089] As it is in Fig. As shown in Figure 7(c), the converter can be switched to intermittent voltage boosting mode to reduce voltage boosting power loss. A longer period during which voltage boosting is stopped produces a greater reduction in loss.

[0090] In step ST25, the control device 500 determines, depending on whether the SOC is within the approval range (the range between the thresholds K1 and K2 according to Fig. 4) or falls outside the scope of approval, whether or not to switch to intermittent voltage boosting mode. The reason why the scope of approval is defined is described below.

[0091] As it is in Fig. As shown in Figure 4, the threshold K1 is defined to ensure that the error dSOC is greater than the lower limit LL. The error dSOC can be considered a margin provided to reduce the accuracy with which the SOC is estimated in the intermittent voltage boosting mode. This margin is intended to reduce the possibility that the control device 500 might erroneously determine that the estimated SOC value is lower than the lower limit LL, when in fact the true SOC value is lower than or greater than the lower limit LL. Consequently, a forced charge based on this erroneous determination can be prevented.

[0092] In contrast, the threshold K2 is defined such that it is smaller than the upper limit UL by the error dSOC. This error dSOC is also given as a margin. Therefore, the probability that the control device 500 will incorrectly determine that the estimated SOC value is greater than the upper limit UL, despite the fact that the true SOC value is the upper limit UL or lower, can be reduced. Accordingly, a forced discharge based on the erroneous determination can be prevented.

[0093] In this way, the range in which the control is permitted in intermittent voltage boost mode can be limited by means of thresholds K1 and K2, thereby reducing the probability of forced charging or discharging, even if the accuracy with which the state of charge (SOC) is estimated is reduced under intermittent voltage boost mode. Consequently, fuel economy can be improved and the user can be prevented from being misled.

[0094] The following describes how the dSOC error is resolved according to Fig. 4 is determined. As described above, the error dSOC is preferably a maximum SOC error that could occur under control in the intermittent voltage boost mode. It is preferable that the maximum possible error be defined as the margin.

[0095] The relationship between the battery current IB, the inductor current IL, and the auxiliary machine current Idc is given by IB = IL + Idc. The auxiliary machine current Idc does not vary depending on the voltage boosting mode. Therefore, the battery current IB1 in the intermittent boosting mode and the battery current IB2 in the continuous voltage boosting mode are expressed by the following equations (1) and (2), respectively, where IL1 is the inductor current in the intermittent voltage boosting mode and IL2 is the inductor current in the continuous voltage boosting mode. IB=lL1+ldc IB2=IL2+Idc

[0096] As it is in Fig. As shown in Figure 7, since the choke current IL2 is constant in the continuous voltage boost mode, the choke current IL2 can be measured accurately. Therefore, if the measurement in the continuous voltage boost mode is used as a reference, a maximum possible error in the measurement of the battery current IB in the intermittent voltage boost mode can occur, as described below.

[0097] In the case where the continuous voltage boost mode is used as a reference, an increase dIB of the battery current IB in the intermittent voltage boost mode is expressed by the following equation (3). dIB=IB1−IB2=IL1−IL2

[0098] In intermittent voltage boosting mode, the inductor current IL1 changes over time, and is a maximum increase of the inductor current IL1 with respect to the inductor current IL2 (IL1max - IL2) (see Fig. 7). dIB⇐IL1max−IL2(dIB is equal to or less than IL1max−IL2)

[0099] The amount of charge (unit: Ah) supplied from battery 150 is obtained by integrating the measured battery current IB (unit: A) over a time period (unit: h) of the intermittent voltage boosting operation. The amount of charge reaches its maximum when the respective times at which the battery current IB is measured coincide with the times at which the choke current IL1 has its maximum value IL1max. Therefore, the maximum value of the amount of charge is given by (IL1max - IL2) × dt (which is given by an area Q0 in Fig. 7 is given). It should be noted that dt is a time interval (the time interval between time (1) and time (4) in Fig. 7) is, which is required for the average ILM of the choke current IL to exceed the threshold TH2 in the intermittent voltage boosting mode.

[0100] Thus, the error dSOC can be expressed by the following equation (5). dSOC=(IL1max−IL2)×dt / C0

[0101] Here, C0 is the capacity C0 (unit: Ah) of the battery 150. Specifically, (IL1max - IL2) × dt is divided by the capacity C0 to convert the amount of charge in the SOC.

[0102] In this way, the dSOC error can be determined to provide sufficient margin to prevent forced charging or discharging, even if the actual charging / discharging of battery 150 is unnecessary. It should be noted that the procedure for determining the dSOC error is not limited to the procedure described above. Second embodiment

[0103] The method for suppressing the operation of converter 200 in the intermittent voltage boost mode is not limited to the method described above in connection with the first embodiment. According to the second embodiment, operation in the intermittent voltage boost mode is suppressed by improving the accuracy with which the battery current IB is measured.

[0104] An electrical system of a hybrid vehicle according to the second embodiment has a configuration that is equivalent to the configuration of the electrical system according to the first embodiment (see Fig. 1 and Fig. 2) Therefore, its description will not be repeated.

[0105] With renewed reference to Fig. As described above in connection with the first embodiment, the switching of the switching elements Q1 and Q2 in the converter 200 in the intermittent voltage boost mode is controlled based on a switching control signal from the control device 500. The amount by which the voltage is boosted per unit of time by the converter 200, namely an increase in the system voltage VH per unit of time (hereinafter also referred to as the recovery rate (unit: V / 2)), is determined as a function of the ratio between an ON period of switching element Q1 and an ON period of switching element Q2. The control device 500 can adjust the recovery rate by means of the switching control signal.

[0106] Fig. Figure 8 shows a graph comparing the battery current IB as a function of the recovery rate. The horizontal axis represents time. The vertical axis represents the system voltage VH, the choke current IL, or the battery current IB. The recovery rate RTS, which is shown in Fig. As shown in 8(b), the recovery rate RTF is smaller than the recovery rate RTF shown in Fig. 8(a) is shown.

[0107] As it is in Fig. As shown in 8(a), in the case where the recovery rate is large, the choke current IL rises sharply. Since the battery current IB is increased by adding the auxiliary machine current Idc (constant value according to Fig. 8) The high recovery rate of the choke coil current IL causes the battery current IB to rise sharply. Since the control device 500 measures the battery current IB in longer cycles than the cycles in which the battery current IB varies, in Fig. 8(a) the value of the battery current IB obtained by the control device 500 may be significantly different depending on the time at which the battery current is measured.

[0108] In contrast, according to the second embodiment, the control device 500 controls the converter 200 using the recovery rate RTS, which is smaller than that in Fig. Figure 8(b) shows. In other words, the control device 500 reduces the rate at which the voltage VB of the battery 150 is increased.

[0109] Accordingly, the battery current IB increases gently, which is why the battery current IB is, in comparison with Fig. 8(a) is averaged over time. As a result, the variation in the value of the battery current IB depending on the time at which the battery current is measured can be reduced. The accuracy with which the SOC is estimated can thus be improved. Accordingly, forced charging or forced discharging, which is actually unnecessary, can be prevented. Variation of the second embodiment

[0110] According to a variation of the second embodiment, the control device 500 limits the choke current IL to a predetermined value or less. In other words, the control device 500 limits the current flowing through the converter 200 in the intermittent voltage boosting mode to a predetermined value or less in order to suppress the operation of the converter 200.

[0111] The choke current IL can be limited to a predetermined value or less by limiting the ratio between one ON period of switching element Q1 and one ON period of switching element Q2 within a certain range, similar to the recovery rate adjustment described above.

[0112] Limiting the choke coil current IL to a predetermined value or less means that the battery current IB is also limited to another predetermined value or less. Accordingly, a sharp increase in the battery current IB is suppressed. As explained above regarding Fig. As described in 8(b), the battery current IB increases gently, which is why the battery current IB is averaged over time. The accuracy with which the SOC is estimated can thus be improved. It should be noted that the choke current IL corresponds to a "current flowing through the voltage boost converter".

[0113] As described above, the first and second embodiments, as well as the variation of the second embodiment, each provide the control that suppresses operation in the intermittent boost mode when the state of charge (SOC) is outside a predetermined range, the control that slows down the recovery rate, and the control that limits the inductor current (IL). These controls can also be combined as required. These controls correspond to all implementations of the "control that suppresses operation of the boost converter in the intermittent boost mode."

[0114] Finally, the following refers again to Fig. 1, Fig. 2 and Fig.4. The present embodiments are summarized. A vehicle power supply unit comprises: the engine 100 and the first power unit 110 (power generation unit); the battery 150; the converter 200, which boosts the voltage of the battery 150 and supplies the boosted voltage to the inverters 210 and 220 (electrical load) of the vehicle; and the control device 500, which controls the converter 200 in continuous voltage boosting mode and intermittent voltage boosting mode. In continuous voltage boosting mode, the converter 200 operates continuously. In intermittent voltage boosting mode, the converter 200 operates intermittently.The control device 500 estimates the state of charge (SOC) of battery 150 based on the battery current IB flowing into and out of battery 150 and forces charging of battery 150 by the power unit 100 and the first motor unit 110 if an estimated SOC value is lower than a predetermined lower limit LL. The control device suppresses operation of the converter 200 in intermittent voltage boost mode to a greater extent when the estimated SOC value is closer to the lower limit LL.

[0115] Preferably, the control device 500 suppresses the operation of the converter 200 in the intermittent voltage boost mode in a case where the estimated value is equal to or less than the threshold K1, which is greater than the lower limit LL.

[0116] Preferably, the threshold K1 is determined such that the threshold is greater than the lower limit LL by a maximum error dSOC of the estimated SOC that can be caused by the operation of the converter 200 in the intermittent voltage boost mode.

[0117] Preferably, the control device 500 suppresses the operation of the converter 200 by preventing the operation of the converter 200 in the intermittent voltage boosting mode.

[0118] Preferably, the control device 500 suppresses the operation of the converter 200 by reducing the rate at which the voltage VB of the battery 150 is increased in the intermittent voltage boosting mode.

[0119] Preferably, the control device 500 suppresses the operation of the converter 200 by limiting the choke current IL of the converter 200 to a predetermined value or less in the intermittent voltage boosting operating mode.

[0120] Although the embodiments of the present invention provide continuous voltage boosting and intermittent voltage boosting modes, continuous voltage bucking and intermittent voltage bucking modes can also be provided. Specifically, the MG-ECU 172 puts the converter 200 into one of the continuous voltage bucking and intermittent voltage bucking modes. In continuous voltage bucking mode, the converter 200 performs a voltage bucking operation without stopping. In intermittent voltage bucking mode, the converter 200 intermittently repeats a voltage bucking operation and a stopping of the voltage bucking operation. When the converter 200 performs the voltage bucking operation, periods in which only switching element Q1 is ON alternate with periods in which both switching elements Q1 and Q2 are OFF.When the converter 200 stops the voltage buck operation, the switching element Q1 is fixed in an ON state and the switching element Q2 is fixed in an OFF state.

[0121] Although the present embodiments have been described with regard to the hybrid vehicle, the present invention is also applicable to a fuel cell vehicle. In this case, a fuel cell unit corresponds to a "power generation unit". Reference symbol list

[0122] 100 Power unit; 110 First motor; 120 Second motor; 112, 122 Neutral point; 130 Power distribution device; 131 Sun gear; 132 Ring gear; 133 Pinion; 134 Carrier; 135 Ring gear shaft (drive shaft); 140 Reduction gear; 150 Battery; 152 Battery sensor; 160 Drive wheel; 170 PM-ECU; 172 MG-ECU; 180 Voltage sensor; 200 Converter; 210, 220 Inverter; 230 SMR; 240 Air conditioning; 500 Control device; PL1, PL2 Positive lead; GL Ground lead; Q1 to Q8 Switching element; D1 to D8 Diode; C1, C2 Capacitor; L Inductor

Claims

[1] Power supply device of a vehicle with a power generation unit (100, 110); a power storage device (150); a voltage boost converter (200) that boosts a voltage of the power storage device (150), the voltage boost converter (200) supplying the boosted voltage to an electrical load (210, 200) of the vehicle; and a control device (500) that controls the voltage boost converter (200) in a continuous voltage boost mode and an intermittent voltage boost mode, wherein in the continuous voltage boost mode the voltage boost converter (200) is operated continuously and in the intermittent voltage boost mode the voltage boost converter (200) is operated intermittently, wherein the control device (500) estimates a state of charge (SOC) of the power storage device (150) based on a current flowing into and out of the power storage device, and the control device (500) instructs the power generation unit (100, 110) to charge the power storage device (150) when an estimated value of the state of charge is lower than a predetermined lower limit (LL), wherein the control device (500) suppresses operation of the voltage boost converter (200) in the intermittent voltage boost mode in a case where the estimated value is equal to or less than a predetermined threshold value (K1) which is greater than the lower limit (LL). [2] The vehicle power supply apparatus according to claim 1, wherein the threshold value (K1) is determined such that the threshold value (K1) is greater than the lower limit (LL) by a maximum error (dSOC) of the estimated value that may be caused by the operation of the voltage boost converter (200) in the intermittent voltage boost mode. [3] The vehicle power supply apparatus according to claim 1 or 2, wherein the control device (500) suppresses the operation of the voltage boost converter (200) by prohibiting the operation of the voltage boost converter (200) in the intermittent voltage boost mode. [4] The vehicle power supply apparatus according to claim 1 or 2, wherein the control device (500) suppresses the operation of the voltage boost converter (200) by reducing a rate (RTS) at which the voltage (VB) of the power storage device (150) is boosted in the intermittent voltage boosting mode. [5] The vehicle power supply apparatus according to claim 1 or 2, wherein the control device (500) suppresses the operation of the voltage boost converter (200) by limiting the current (IL) flowing through the voltage boost converter (200) in the intermittent voltage boost mode to a predetermined value or less.

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